1. Field of the Invention
The present invention relates to improvements in rebound property of a baseball or softball bat.
2. Description of the Background Art
Baseball or softball bats (hereinafter, referred to as a “bat”) made of various materials are commercially available. Some are made of wood or metal such as titanium, titanium alloy, aluminum alloy or the like. Others are made of fiber-reinforced plastic in which a matrix resin is impregnated and cured in carbon fiber, glass fiber or the like.
When a bat is structured with only one of those materials, however, it is difficult to change a property value of the bat to a large extent. Therefore, a bat made from a combination of various materials has been developed.
In order to achieve a significant change in a value of rebound property of the bat, a variety of bats coated with an elastic body have been developed. For example, Japanese Patent Laying-Open No. 62-106784 discloses a cushion bat with a shape identical to a conventional one, of which core portion extending to entire length thereof is coated with an elastic body. Japanese Utility Model Laying-Open No. 63-156667 discloses a bat packed with a rubber sponge, having two rubber sponges bonded to a wooden core. In addition, Japanese Patent Laying-Open No. 2000-153013 discloses a baseball bat, in which a circumferential surface of a core member made of light metal pipe is coated with an elastic body except for a grip portion. Further, Japanese Patent Laying-Open No. 7-275413 discloses a ball-game bat, in which a core member made of carbon fiber is coated with a hard urethane layer, and a protection layer composed of glass fiber having a synthetic resin impregnated is provided thereon.
In the bats disclosed in Japanese Patent Laying-Open No. 62-106784, Japanese Utility Model Laying-Open No. 63-156667 and Japanese Patent Laying-Open No. 2000-153013, an object of coating with an elastic body is to obtain a bat capable of lowering the impact and vibration in ball-hitting, and suppressing a hit distance of the ball for safe use. Accordingly, the elastic body is used, having a physical property that will suppress the hit distance. These bats are suited, for example, for a use in a narrow space, hitting table tennis ball, or toss batting. Moreover, an object of Japanese Patent Laying-Open No. 7-275413 is to reduce manufacturing cost as well as to improve manufacturing process and a method of adjusting weight and “crack” in hitting the ball. Therefore, appearance and rebound property are not changed at all, compared with a conventional bat.
On the other hand, a baseball or softball bat is required to have durability and a property to carry the ball far. The conventional bat as described above is not satisfactory for such requirements.